(AFP) - Barack Obama and Narendra Modi vowed to transform skeletal US-India security relations into an "anchor of stability" at the White House on Tuesday.

Obama offered his guest a warm embrace, arguing it was "natural" that two of the world's largest democracies should cooperate.

The visit was another symbolic marker on India -- and Modi's -- long walk in from the cold.

Obama notably put his shoulder behind Modi's bid for access to missile technology and nuclear commerce.

The two leaders also finalized agreements on military logistics and sharing "terrorist screening information."

"The US-India defense relationship can be an anchor of stability," a joint statement declared.

There was also a step toward better cybersecurity cooperation, which experts say is crucial to protect outsourced US information technology.

For decades, US-India relations had been beset by lingering Cold War enmity and India's controversial development of a nuclear bomb.

In 2005, president George W. Bush begun the thaw by lifting a three-decade long moratorium on nuclear cooperation with India.

Obama went one step further, urging nuclear powers to readmit India to a group of countries permitted to trade sensitive nuclear materials.

"We discussed the progress that we have made around civil nuclear energy and I indicated our support for India becoming part of the nuclear suppliers group," Obama said.

That public display of support is likely to be noted in Beijing, which has been skeptical about India's readmission.

Beijing sees India as a potential regional rival and closer India-US relations as a potential check on its power.

Obama also hailed an agreement for US firm Westinghouse to build six nuclear reactors in India.

- Strange bedfellows -

When Obama entered the White House in 2009, Modi was effectively banned from visiting the United States for his role in anti-Muslim riots that killed hundreds.

Obama's leaves office with Modi transformed from persona non grata to celebrated guest.

This was his fourth visit to the United States.

On Wednesday Modi will address a prestigious joint meeting of Congress for the first time.

The speech will be the fifth such address by an Indian premier, and the first in more than a decade.

It comes at pivotal time, when the body is blocking the sale of F-16 fighters to India's arch rival Pakistan.

But turning warm words into concrete agreement has proven difficult.

"There is always a lot of happy talk," said Michael Kugelman of the Wilson Center.

"The happy talk sometimes detracts from the fact that things do move along quite slowly."

A proposed bilateral investment treaty has languished for years, as New Delhi has taken a tough negotiating line.

Modi, who faces reelection in 2019, has pegged his political future on a reform agenda and boosting the economy.

He has also made nuclear energy a priority, in part to offset horrendous levels of air pollution.

Coal-fired power plants are a dominant power source.

But Modi has also been a reluctant backer of measures to tackle climate change.

India fears carbon reduction could entail a price tag that harms growth.

Obama said the two men had "discussed how we can as quickly as possible bring the Paris (climate) agreement into force."

But there appeared to be no firm agreement on when that would happen.

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